Transducer cover, method for forming the cover, and ultrasonic medical instrument with the cover

ABSTRACT

A transducer cover for use in an ultrasonic medical instrument having a transducer is disclosed. The transducer cover includes a vibration absorbing layer of a generally cylindrical form made of a synthetic resin having a vibration absorbing property, and a chemical blocking layer of a generally cylindrical form made of a synthetic resin which is impermeable to water and chemicals. The vibration absorbing layer and the chemical blocking layer are coaxially laminated, and capable of sealing arrangement over and around the transducer. Also disclosed is an ultrasonic medical instrument having an ultrasonic transducer and the transducer cover, and a method for forming the transducer cover over and around an ultrasonic transducer of an ultrasonic medical instrument.

FIELD OF ART

The present invention relates to a transducer cover for use in anultrasonic medical instrument, such as an ultrasonic handpiece, as wellas to a method for forming the transducer cover, and an ultrasonicmedical instrument with the transducer cover.

BACKGROUND ART

In the medical art, ultrasonic handpieces employing a piezoelectricelement (ultrasonic transducer) have hitherto been used for treatment ofliving tissues, such as cutting or removal of bones or teeth. As anexample of such ultrasonic handpieces, JP-2005-95243-A1 discloses anultrasonic handpiece for dental treatment, which is used for endodontictherapy, such as treatment of pulpal diseases and periapicalperiodontitis, or removal of tartar. The ultrasonic handpiece disclosedin this publication has an ultrasonic generator in a cylindrical bodycasing, and a tip attached to the distal end of the body casing andvibrated by the ultrasonic generator.

In general, this type of ultrasonic generator has, as shown in FIG. 7,front horn 71 located in the distal part of the body casing, rear horn72 connected to the front horn 71 and located in the proximal part ofthe body casing, and transducer 73 arranged and held between the frontand rear horns 71 and 72. In order to fix the ultrasonic generator inthe body casing, and to block or reduce transmission of vibration of thetransducer 73 to the body casing during treatment, transducer cover 74is attached over and around the transducer 73. The transducer cover 74used for this type of handpiece is usually an annular molded rubberproduct having elasticity, and fits over and around the transducer 73.The ultrasonic generator is placed in the body casing via the transducercover 74, and a connector is connected to the proximal end of the bodycasing for supplying power and cooling water to the ultrasonicgenerator. When powered, the transducer 73 generates ultrasonicmechanical vibration, which is amplified by the front horn 71 andtransmitted to the tip to vibrate the tip in the longitudinal directionof the front horn 71.

In clinical practice, tools and devices used in treatment are subjectedto various sterilization processes after each treatment in order toprevent infection with various pathogenic bacteria among patients.Ultrasonic handpieces are not an exception and are usually subjected tohigh pressure steam sterilization such as autoclaving. To this end, thetransducer cover used in ultrasonic handpieces is made of silicon rubberor the like material having excellent resistance to water, heat, andchemicals, so as to prevent steam and chemicals from permeating throughthe transducer cover and adhering to the electrodes of the transducer,which causes insulation deterioration of the transducer.

In order to enhance prevention of infection with various pathogenicbacteria among patients via medical tools and devices, it is recentlyrecommended to subject the tools and devices to washing with hot watercontaining alkaline chemicals, in addition to the conventional highpressure steam sterilization or other sterilization.

However, when ultrasonic handpieces are washed with hot water containingalkaline chemicals, the chemicals often permeate the transducer covereven if it is made of silicon rubber, and adhere to the electrodes ofthe transducer to cause insulation degradation of the transducer. As aresult, ultrasonic vibration is weakened and the original performancecannot be delivered.

Ultrasonic handpieces are also subjected to washing with hot watercontaining acidic chemicals, or immersion cleaning in alkaline or acidicchemicals. These procedures also have similar problems as describedabove.

SUMMARY OF THE INVENTION

It is an object of the present invention to securely block thepermeation of chemicals into the transducer cover of an ultrasonicmedical instrument which is subjected to washing with hot watercontaining alkaline or acidic chemicals or immersion cleaning inalkaline or acidic chemicals, and to securely prevent insulation failureof the transducer caused by adhesion of the chemicals to the electrodesof the transducer.

According to the present invention, there is provided a transducer coverfor use in an ultrasonic medical instrument having a transducer,comprising:

a vibration absorbing layer of a generally cylindrical form made of asynthetic resin having a vibration absorbing property, and

a chemical blocking layer of a generally cylindrical form made of asynthetic resin which is impermeable to water and chemicals,

wherein said vibration absorbing layer and said chemical blocking layerare coaxially laminated, and capable of sealing arrangement over andaround the transducer.

Of the two coaxial layers, the vibration absorbing layer may be theinner layer, and the chemical blocking layer may be the outer layer.

The chemical blocking layer may extend beyond the vibration absorbinglayer at least distally to cover the distal end of the vibrationabsorbing layer.

The vibration absorbing layer may be made of rubber having a vibrationabsorbing property. The chemical blocking layer may be made of rubberhaving resistance to water, heat, and chemicals, and renderedimpermeable by compression molding.

According to the present invention, there is also provided an ultrasonicmedical instrument comprising:

an ultrasonic transducer for generating vibration, and

a transducer cover arranged over and around the ultrasonic transducer,said transducer cover comprising:

a vibration absorbing layer of a generally cylindrical form made of asynthetic resin having a vibration absorbing property, and

a chemical blocking layer of a generally cylindrical form made of asynthetic resin which is impermeable to water and chemicals,

wherein said vibration absorbing layer and said chemical blocking layerare coaxially laminated and sealingly attached over and around theultrasonic transducer.

The vibration absorbing layer may be sealingly attached to theultrasonic transducer as the inner layer, and the chemical blockinglayer may be sealingly attached to the vibration absorbing layer as theouter layer.

The chemical blocking layer may extend beyond the vibration absorbinglayer at least distally to cover the distal end of the vibrationabsorbing layer.

The vibration absorbing layer may be made of rubber having a vibrationabsorbing property. The chemical blocking layer may be made of rubberhaving resistance to water, heat, and chemicals, and impermeable towater and chemicals.

According to the present invention, there is further provided a methodfor forming a transducer cover over and around an ultrasonic transducerof an ultrasonic medical instrument, comprising:

arranging a cylindrical member around the ultrasonic transducer, saidcylindrical member being made of a synthetic resin impermeable to waterand chemicals,

arranging an elastic, thermosetting synthetic resin material in liquidform inside or outside of said cylindrical member in contact therewithto form a layer,

vacuum defoaming said synthetic resin in liquid form, and

thermally curing said synthetic resin in liquid form,

whereby a transducer cover having a vibration absorbing layer and achemical blocking layer is formed sealingly laminated over and aroundthe ultrasonic transducer.

The above step of arranging the synthetic resin material in liquid formmay be carried out by introducing the synthetic resin material in liquidform between the cylindrical member and the ultrasonic transducer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of an embodiment of anultrasonic handpiece having a transducer cover according to the presentinvention.

FIG. 2 is an exploded side view showing the body casing, ultrasonicgenerator, and tip of the ultrasonic handpiece of FIG. 1.

FIG. 3 is an enlarged longitudinal sectional view of the ultrasonicgenerator and the transducer cover of the ultrasonic handpiece of FIG.1.

FIG. 4 illustrates how the transducer cover of the ultrasonic handpieceof FIG. 1 is formed.

FIG. 5 is an enlarged longitudinal sectional view of the transducercover of the ultrasonic handpiece of FIG. 1, showing its two-layeredstructure.

FIG. 6 is an enlarged longitudinal sectional view similar to FIG. 5,showing another embodiment of the transducer cover.

FIG. 7 is an enlarged longitudinal sectional view showing the structureof a conventional transducer cover.

FIG. 8 is an enlarged longitudinal sectional view of the vibrationabsorbing layer of the embodiment of the transducer cover of FIG. 5.

FIG. 9 is an enlarged longitudinal sectional view of the chemicalblocking layer of the embodiment of the transducer cover of FIG. 5.

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention will now be explained in detail with reference tothe preferred embodiments taken in conjunction with the attacheddrawings.

FIG. 1 illustrates an ultrasonic dental handpiece equipped with atransducer cover according to the present invention. Ultrasonichandpiece 1 has body casing 10. To the distal end of the body casing 10is detachably attached dental tool tip 3, while to the proximal end isdetachably attached connector 4 for providing connection to a powersource and a cooling water source. Ultrasonic generator 2 is containedin the body casing 10, and provided with power and cooling water via theconnector 4.

The body casing 10 is composed of case 11 and cap 12 connected to thedistal end of the case 11, as shown in FIG. 2. The case 11 is generallyin the form of a slightly distally tapered hollow cylinder, and has anannular projection of a reduced diameter on its distal end and athreaded inner surface 112 at its proximal end. The circumferentialsurface of the annular projection is formed with thread 111. The cap 12is generally in the form of a distally tapered hollow cylinder, and hassmall opening 120 at its distal end for receiving the tip 3 therein andlarge opening at its proximal end for receiving the distal end portionof the case 11. Thread 121 is formed in the inner surface of the cap 12in its proximal end portion so as to mesh with the thread 111 on thecase 11. In this way, the case 11 and the cap 12 are detachablyconnected via the threads 111 and 121.

As shown in FIGS. 2 and 3, the ultrasonic generator 2 has front horn 21,rear horn 22, connecting member 23 connecting these two horns 21 and 22,and transducer 25 held between the front and rear horns 21 and 22 andarranged around the connecting member 23 via insulator tube 24.

The front horn 21 has a distally tapered contour so as to fit in the cap12, and has plug 211 at its distal end, on which the tip 3 is to befitted. Water channel 212 is formed through the front horn 21 along theaxial center thereof with an enlarged proximal portion, which is formedwith thread 213. The rear horn 22 has a generally cylindrical contour soas to fit in the case 11, and has connector port 221 on its proximalend. Water channel 222 is formed through the rear horn 22 along theaxial center thereof with an enlarged distal portion, which is formedwith thread 223. The connector port 221 forms a proximal extension ofthe water channel 222.

The connecting member 23 is a connecting rod generally in the form of acylinder having a diameter smaller than those of the front and rearhorns 21 and 22. Water channel 232 is formed through the connectingmember 23 along the axial center thereof for providing fluidcommunication between the water channels 212 and 222 of the front andrear horns 21 and 22. The connecting member 23 has a distal portionwhich is threaded 231 on the outer surface so as to mesh with the thread213 in the proximal end portion of the front horn 21, a proximal portionwhich is threaded 233 on the outer surface so as to mesh with the thread223 in the distal end portion of the rear horn 22, and a middle portionforming a surface on which the transducer 25 is attached. The insulatortube 24 fits on the middle portion. The transducer 25 is in an annularform, and is arranged around and attached to the middle portion of theconnecting member 23 with the insulator tube 24 interposed between thetransducer 25 and the connecting member 23. Lead wires extend fromelectrodes of the transducer 25.

O-ring 26 is fitted on each end of the connecting member 23, and theconnecting member 23 is screwed together with the front horn 21 with thedistal thread 231 meshing with the proximal thread 213, and with therear horn 22 with the proximal thread 233 meshing with the distal thread223. In this way, the front horn 21 and the rear horn 22 are connectedvia the connecting member 23, and the transducer 25 fitted around theconnecting member 23 on its middle portion via the insulator tube 24 isarranged and held between the front and rear horns 21 and 22.

Transducer cover 5 is provided over and around the transducer 25 so asto fix the ultrasonic generator 2 in the body casing 10 and to block orat least reduce transmission of vibration of the transducer 25 to thebody casing 10. The ultrasonic generator 2 provided with the transducercover 5 is then placed in the body casing 10. At the ends of the leadwire s extending from the transducer 25, terminals are connected, whichare arranged in the proximal opening of the case 11.

Tip 3 is available in various forms as is well known in the art, so thatdetailed discussion about its form is eliminated. In any case, theproximal portion of the tip 3 forms attachment end 30, which is formedgenerally in a cylindrical form sized and shaped to be inserted into thedistal opening 120 of the cap 12 and fitted onto distal plug 211 of thefront horn 21. The tip 3 is inserted into the distal end of the bodycasing 10 and operatively connected to the ultrasonic generator 2.

Referring back to FIG. 1, connector 4 has connector case 40, which has aproximally tapered, generally cylindrical form, and has an annularprojection at the distal end, which has a smaller diameter and is formedwith thread 401 on its outer surface. In the proximal end of theconnector case 40 is formed opening 402, in which connector pipe 404 isinserted, and opening 403, in which connector pipe 405 is inserted. Oneend of the connector pipe 404 outside the connector case 40 is connectedto the cooling water tube 41 extending from the water source, and theother end inside the connector case 40 is connected to cooling watertube 43 to be connected to the ultrasonic generator 2. The connectorpipe 405 receives therein power supply cable 42 extending from the powersource. Wiring 421 bundled in the power supply cable 42 is connected toterminals 422, which are arranged in the distal opening of the connectorcase 40.

Next, the transducer cover 5 used in the handpiece 1 is explained indetail. Referring to FIGS. 2 and 3, the transducer cover 5 has at leasttwo coaxial layers, namely, vibration absorbing layer 51 made of asynthetic resin having a vibration absorbing property, and chemicalblocking layer 52 made of a synthetic resin which is impermeable towater and chemicals. These two layers have a first axial through-channel51A and a second axial trough-channel 51B, respectively, and are sealinglaminated over and around the transducer 25.

The vibration absorbing layer 51 is made of rubber, such as siliconrubber, having a vibration absorbing property. The chemical blockinglayer 52 is made of rubber, such as silicon rubber, having resistance towater, heat, and chemicals, and rendered impermeable by compressionmolding. The chemical blocking layer 52 extends beyond the vibrationabsorbing layer 51 at least distally to cover the distal end of thevibration absorbing layer 51 and be sealingly attached to the front horn21. In this way, the layers 51 and 52 are sealingly laminated around thetransducer 25, with the vibration absorbing layer 51 being the innerlayer and the chemical blocking layer 52 being the outer layer.

FIG. 4 illustrates how this transducer cover 5 is formed. First, asshown in FIGS. 4(1) and 4(2), cylindrical member 520 made of a syntheticresin which is impermeable to water and chemicals, is arranged aroundthe transducer 25 (Step 1). In this embodiment, the cylindrical member520 is made of compression silicon rubber. The cylindrical member 520has an enough length to enclose the entire transducer 25, with thedistal end reaching the circumferential surface of the front horn 21 andthe proximal end reaching the circumferential surface of the rear horn22. The cylindrical member 520 is distally tapered so that the distalend is sealingly attached to the front horn 21.

Next, as shown in FIG. 4 (3), an elastic, thermosetting synthetic resin,in this case silicon rubber 510 in liquid form, is poured inside thecylindrical member 520 to form a layer between the transducer 25 and thecylindrical member 520 in contact therewith (Step 2). Then, the siliconrubber 510 in liquid form is vacuum defoamed as shown in FIG. 4 (4)(Step 3), and thermally cured as shown in FIG. 4(5) (Step 4).

Through these Steps 1 to 4, the transducer cover 5 is formed over andaround the transducer 25 by sealingly laminating the vibration absorbinglayer 51 and the chemical blocking layer 52. Here, the chemical blockinglayer 52 extends distally beyond and covers the distal end of thevibration absorbing layer 51 and is sealingly fixed on thecircumferential surface of the front horn 21, and extends proximallytogether with the vibration absorbing layer 51 to the circumferentialsurface of the rear horn 22.

The ultrasonic generator 2, on which the transducer cover 5 is thusformed around the transducer 25, is then placed in the body casing 10 asshown in FIG. 1. The transducer cover 5 is compressed between the innersurface of the case 11 and the outer surface of the transducer 25, andby means of the elastic restoration of the transducer cover 5, theultrasonic generator 2 is snugly fixed in the body casing 10.

Then the connector 4 is connected to the proximal end of the body casing10 via O-ring 44, by which the cooling water tube 43 in the connector 4is connected to the connector port 221 forming an extension of the waterchannel 222 in the ultrasonic generator 2, and the wiring 421 in theconnector 4 is connected via the terminals to the lead wires extendingfrom the transducer 25. The proximal thread 112 on the inner surface ofthe body casing 10 meshes with the distal thread 401 on the outersurface of the connector 4 to connect the body casing 10 and theconnector 4.

In the ultrasonic handpiece 1, as shown in FIG. 5, the transducer cover5 has the vibration absorbing layer 51 and the chemical blocking layer52, which are sealingly laminated around the transducer 25, with thevibration absorbing layer 51 sealingly attached to the transducer 25 andthe chemical blocking layer 52 sealingly attached to the vibrationabsorbing layer 51. The vibration absorbing layer 51 absorbs vibrationof the transducer 25 to block or at least reduce transmission of thevibration to the body casing 10. The chemical blocking layer 52 blockspermeation of liquid, such as chemicals. Thus even when the ultrasonichandpiece 1 is subjected to washing with hot water containing alkalineor acidic chemicals in addition to autoclaving or other sterilizationtreatment, permeation of chemical s maybe securely blocked due to theimpermeability of the chemical blocking layer 52. The transducer cover 5is also effective in immersion cleaning in alkaline or acidic chemicals.While the conventional properties such as vibration absorption andresistance to water, heat, and chemicals are maintained, the transducercover 5 is rendered impermeable to water and chemicals. Thus insulationfailure of the transducer 25 caused by permeation and adhesion ofchemicals to the electrodes of the transducer 25 may securely beprevented.

Further, since the vibration absorbing layer 51 and the chemicalblocking layer 52 are laminated with the former being the inner layerand the latter being the outer layer, even when the ultrasonic handpieceis subjected to cleaning with hot water containing alkaline or acidicchemicals, or immersion cleaning in alkaline or acidic chemicals, thechemicals are blocked by the outer chemical blocking layer 52 and willnot reach the vibration absorbing layer 51. Since the chemical blockinglayer 52 extends beyond the vibration absorbing layer 51 at leastdistally to cover the distal end of the vibration absorbing layer and besealingly attached to the front horn 21, the chemicals will not enterthrough the distal end of the vibration absorbing layer 51.

The method for forming the transducer cover 5 according to the presentinvention includes the steps of arranging the cylindrical member 520made of a synthetic resin impermeable to water and chemicals around thetransducer 25, arranging the elastic, thermosetting synthetic resinmaterial in liquid form inside the cylindrical member 520 in contacttherewith to form a layer, vacuum defoaming the synthetic resin inliquid form, and thermally curing the synthetic resin in liquid form.Through these steps, the transducer cover 5 having a vibration absorbinglayer 51 which absorbs vibration of the transducer 25 to block or atleast reduce transmission of the vibration to the body casing 10, and achemical blocking layer 52 which blocks permeation of liquid containingchemicals, is formed sealingly laminated over and around the transducer25. Thus, the transducer cover 5 having the vibration absorbing layer 51and the chemical blocking layer 52 may be securely and easily providedover and around the transducer 25. By introducing the synthetic resin510 in liquid form inside the cylindrical member 520, a mold or the likemeans for holding the resin 510 in liquid form may be eliminated, tofacilitate formation of sealingly laminated vibration absorbing layer 51and the chemical blocking layer 52. In the embodiment described above,the transducer cover 5 has two layers, namely, vibration absorbing layer51 and the chemical blocking layer 52. However, the transducer cover 5may have three or more layers including a plurality of the vibrationabsorbing layer 51 and/or the chemical blocking layer 52, or includingan additional layer having resistance to water, heat, and chemicals,inside, outside, or between the vibration absorbing layer 51 and thechemical blocking layer 52. With such a structure, the above effects ofthe transducer cover 5 may further be improved. In the embodimentdescribed above, the vibration absorbing layer 51 is laminated as theinner layer and the chemical blocking layer 52 is laminated as the outerlayer around the transducer 25. However, as shown in FIG. 6, thechemical blocking layer 52 may be laminated as the inner layer and thevibration absorbing layer 51 may be laminated as the outer layer. Evenwith this structure, nearly the same effects as described above may beachieved.

For forming a transducer cover of this structure, the cylindrical member520 is sized so as to sealingly contact over and around the transducer25, and the elastic, thermosetting, synthetic resin 510 in liquid formmay be introduced into a mold arranged around the cylindrical member520, to form a layer of the resin 510 around the cylindrical member 520in contact therewith.

The vibration absorbing layer 51 in the above embodiment is made ofsilicon rubber, but may alternatively be made of other rubber materialor other synthetic resin as long as the material absorbs vibration ofthe transducer. Similarly, the chemical blocking layer 52 in the aboveembodiment is made of compression silicon rubber, but may alternativelybe made of other compression rubber or other synthetic resin as long asthe material is impermeable to water and chemicals. Even with suchstructure, the same effects as described above may be achieved. Further,the chemical blocking layer 52 may be produced by coating a syntheticresin layer having resistance to water, heat, and chemicals, with animpermeable material, or by overlaying and adhering an impermeablematerial layer to a synthetic resin layer having resistance to water,heat, and chemicals.

Further, the chemical blocking layer 52 may extend beyond the vibrationabsorbing layer 51 also proximally to cover the proximal end of thelatter and be sealingly adhered to the rear horn 22. With such astructure, the above effects may further be improved.

What is claimed is:
 1. A transducer cover for use in an ultrasonicmedical instrument having a transducer, comprising: a vibrationabsorbing layer of a hollow-cylindrical form having a first axialthrough-channel, and made of a synthetic resin having a vibrationabsorbing property, and a chemical blocking layer of ahollow-cylindrical form having a second axial through-channel, and madeof a synthetic resin which is impermeable to water and chemicals,wherein said vibration absorbing layer and said chemical blocking layerare coaxially laminated, and in a sealing arrangement over and aroundthe transducer along a longitudinal axis of the transducer, and saidtransducer is arranged inside the first axial through-channel and insidethe second axial through-channel, wherein said vibration absorbing layeris an inner layer and said chemical blocking layer is an outer layer,with said chemical blocking layer sealingly attached to said vibrationabsorbing layer, wherein said chemical blocking layer extends beyondsaid vibration absorbing layer at least distally to cover a distal endof the vibration absorbing layer, and wherein said chemical blockinglayer extends beyond said vibration absorbing layer also proximally tocover a proximal end of the vibration absorbing layer.
 2. The transducercover according to claim 1, wherein said vibration absorbing layer ismade of rubber having a vibration absorbing property.
 3. The transducercover according to claim 1, wherein said chemical blocking layer is madeof rubber having resistance to water, heat, and chemicals, and renderedimpermeable by compression molding.
 4. The transducer cover according toclaim 1, wherein said vibration absorbing layer does not extend beyondsaid chemical blocking layer either distally or proximally.